Mechanism of bare patch formation under Haloxylon ammodendron canopies and patch effects on soil microorganisms in the Gurbantunggut Desert, Northern China

Abstract

Background and aims In the Gurbantunggut Desert, Haloxylon ammodendron and Syntrichia caninervis are often found at the base of the dunes. In these areas, bare patches usually form under the H. ammodendron canopy, but not under other shrub canopies. Methods We compared the soil chemical properties under H. ammodendron canopy inside the bare patches (UC) and of soil under moss crust outside of H. ammodendron canopy bare patches (UM), and used UHPLC-MS/MS to analyze soil metabolites and metagenomic sequencing to characterize the structure of soil microflora. Results A total of 951 metabolites were identified in the soil samples, and 518 differential metabolites were observed. The content of amides, such as oleamide, in UC soil was significantly higher than that in UM soil, suggesting that the amides may be the main allelochemicals inhibiting S. caninervis. The differences in soil chemical properties and metabolites impacted soil microorganisms, but the structure and function of microbial communities did not differ significantly. Conclusions The amides secreted by H. ammodendron roots create a concentration gradient under its canopy, with high concentrations inhibiting S. caninervis, causing changes in soil chemical factors inside and outside the bare patch. These changes affect the abundance of microbial species and relevant metabolic pathways. The differences in microbial communities and functions are caused by a combination of soil chemical properties and metabolites, rather than a direct effect of high levels of soil metabolites such as amides.

Study on the Dynamics of Stem Sap Flow in Minqin Wind and Sand Control Haloxylon ammodendron Forest, China

“…The main factors affecting the changes in stem sap flow of H. ammodendron differed due to different monitoring time and space scales. According to previous studies, the instantaneous change of H. ammodendron sap flow rate is mainly affected by meteorological factors, while soil temperature and humidity have little impact on the change in trunk sap flow rate at the daily scale, but there is a significant correlation between the time scale of seasons and the daily average sap flow rate [31,32]. In this study, we set up the simultaneous monitoring of H. ammodendron sap flow in different age sections, focusing on H. ammodendron growth processes and inter-individual variability at larger spatial and temporal scales, and minimizing the influence of meteorological environmental factors.…”

“…The highest rainfall occurred in September, while the average water consumption of the four age classes of H. ammodendron was low, because the temperature decreased in September and the content of abscisic acid in H. ammodendron reached the highest [29]. The increase in abscisic acid encouraged H. ammodendron to enter a dormant state [30,31], resulting in the low water consumption of H. ammodendron. The correlation between the stem sap flow of four age classes of H. ammodendron in June and various meteorological factors is not significant.…”

Effects of groundwater depth on ecological stoichiometric characteristics of assimilated branches and soil of two desert plants

“…The foliage of H. persicum and H. ammodendron is degraded, and litter production is much lower than the national average ( An and Li, 2014 ). Soil microbial diversity and biomass are also significantly reduced in arid habitats, and nutrient turnover is slower ( Liu et al., 2022 ). Plants living in barren habitats always have a higher nutrient acquisition cost, so there is often a resorption of nutrients in senescing withered parts, which implies the adaptability of desert plants ( Veneklaas et al., 2012 ).…”

“…In addition, H. ammodendron absorbs excess salt ions from the soil to maintain osmotic pressure for survival ( Xi et al., 2004 ). Changes in microbial abundance and metabolic pathways in soil lead to lower turnover rates, then increase accumulation of carbon and nitrogen ( Liu et al., 2022 ). The low C:N under the H. ammodendron canopy allows for faster release of N and facilitates uptake ( An and Li, 2014 ), which may explain why both STN and LTN of H. ammodendron are significantly greater than those of H. persicum .…”